Due to the effect of deterioration and corrosion, large amounts of oil and gas pipeline segments need to be replaced in offshore platforms every year. By using traditional reconstruct method, it needs to stop production in offshore platform firstly, then follows insulation, backout, baiting, jointing, installation, pressure test for tightness, etc. This process will take a long time and much work, and it will greatly influence the regular manufacture of oil and gas. In this work, a new method is introduced that oil and gas pipeline segments are replaced without stopping production. The technology includes precisely measuring geometry dimension of the oil and gas pipeline segments to be replaced, making prefabricate replacement segments exactly offline, and replacing the pipeline segments on site in a speedy and safety way. Last, an engineering applications case is given to show the whole detail process. It proves that the technology not only makes great progress in pipeline reconstruction, but also results in good social and economic benefits.